1. Field of the Invention
The present invention relates to a method for improving image quality, and more particularly, to an image processing method which performs an edge enhancement process after performing a de-blocking process.
2. Description of the Prior Art
Currently, as defined in most video encoding specifications, pixel data of a video picture is usually encoded in units of blocks (e.g., each block is 4 by 4 pixels). A quantization operation of each block is required for increasing the compression ratio of the pixel data. As a result, after being decoded, the block-based video picture has blocking effects, which are discontinuity effects around boundaries between the blocks.
In order to decrease the severity of the blocking effect to improve the quality of block-based video pictures, the H.264 specification, which is a newly introduced video encoding specification, calculates boundary strength to determine discontinuity extent among blocks, utilizes thresholds of quantization parameters to check if the discontinuous edge is a real edge or a blocking effect, and finally provides filters with different strengths to process edges correspondingly. Please refer to the H.264 specification for more information. Although video pictures processed by the de-blocking process of H.264 have good picture quality, the H.264 specification requires complex calculation, which is one of its drawbacks.